Introduction to Cryptography
This is old technology first attributed to Julius Caesar who used the nifty cipher which replaced every letter with that three letters further in the alphabet
- So A becomes D and Z becomes C (using cyclic wraparound)
Most ciphers involve an algorithm and a parameter (this is 3 in the above) where usually algorithm can be public but parameter is kept secret and is called a key
- key needs to be quite big to be safe (say at least 40 bits long)
- It is usually not possible to keep algorithm secret and in fact making it public can encourage experts to examine and comment on its reliability (i.e. ease of breaking)